Two novel mouse genes mapped to chromosome Yp are expressed specifically in spermatids

Abstract

The male-specific region of the Y chromosome is evolutionarily predisposed to accumulate genes important for spermatogenesis. Recent work in this laboratory identified two novel Y-linked transcripts that were upregulated in the testis in response to deletions on the chromosome arm Yq. This article reports the further characterisation of these two transcripts and their comparison to related X and autosomal genes. Both map to chromosome arm Yp, outside the Sxr ( b ) deletion interval, both are present in at least two copies on the Y, and both are expressed specifically in spermatids. Given the testicular phenotype of mice with deletions on the Y chromosome, both genes are therefore likely to function in spermatid differentiation. AK006152 is a novel mouse-specific gene with a single potential open reading frame, and it is unusual in that there appears to be no X-linked relative. H2al2y is a novel histone in the H2A superfamily and has multiple X-linked relatives and a single autosomal relative in mouse. The presence of a single X-linked copy in rat suggests that H2al amplification is mouse-specific, with the alternative explanation being an earlier amplification followed by gene loss. A phylogenetic analysis of H2al genes together with other H2A genes indicates that H2al is most closely related to the mammalian-specific H2A.Bbd family of histones. Interestingly, K (a)/K (s) analysis indicates that the X and Y members of the H2al family may be under positive selection in mouse, while the autosomal copy is under purifying selection and presumably retains the ancestral function.

The Multicopy Gene Sly Represses the Sex Chromosomes in the Male Mouse Germline after Meiosis

“…In our microarray screening, several autosomal and sex-linked genes coding for histones H2, H3, and H4 variants (including recently identified spermatid-specific H2A variants, H2al1 and H2al2y [45],[46]) were found up-regulated when Sly expression is reduced. Conversely, Chaf1b , which encodes a chromatin assembly factor, appears down-regulated.…”

Mouse Y-Linked Zfy1 and Zfy2 Are Expressed during the Male-Specific Interphase between Meiosis I and Meiosis II and Promote the 2nd Meiotic Division

“…The protein-coding gene content of Sxr b is thought to be limited to a few copies of Rbmy , two copies of H2al2y , Sry and a Zfy2/1 fusion gene spanning the Sxr b deletion breakpoint [7], [20], [21]. Because interphasic secondary spermatocytes are a very transient cell type in normal testes, there is no published information on expression of these genes at this stage.…”

Deficiency of the multi-copy mouse Y gene Sly causes sperm DNA damage and abnormal chromatin packaging

“…Nevertheless, several genes appear to be promising individual candidates. For instance, alteration in the expression of H2al1 and H2al2y genes (Ferguson et al, 2009), which encode spermatid specific histone variants (Govin et al, 2007), could affect sperm chromatin protamination and therefore spermiogenesis. A few autosomal genes were also downregulated in Sly-deficient spermatids ).…”